Today's mobile computing environment requires the ability to seamlessly route communication content associated with nodes that routinely connect to a data network at different points of attachment, e.g., via air and wireline interfaces. Such nodes include cellular telephones, Personal Digital Assistants (PDAs), laptop computers, and other mobile wireless communication equipment.
In one example, a mobile node may wirelessly and continuously be connected to a network infrastructure using the same Internet Protocol (IP) address regardless of the mobile node's physical location. The mobile node may be identified by a home address associated with the mobile node's home network. When the mobile node connects to the network infrastructure, the mobile node is identified by the home address and by at least one care-of-address.
Information sent across the network infrastructure to the mobile node's home address is transparently routed to the mobile node's care-of-address. The information destined for the mobile node's home address is received at the home link by a home gateway or router that tunnels the information to the mobile node's care-of address via an IP tunnel.
As the mobile node changes its physical location or connects to a different network interface (e.g., wireline or wireless) and switches to a different foreign gateway or router to maintain connectivity to the network infrastructure, the mobile node updates the home gateway or router with its new care-of address. In this way, the mobile node can relocate, connect to various foreign gateways or routers, and maintain a constant IP address presence without interruptions or disturbances in network connectivity.
However, when the mobile node switches between two different network interfaces while an IP application is running, the IP connection is interrupted at the moment the mobile node leaves the old network link. This connection is interrupted at least until at the mobile node the new link to the network has been made and until the new location, i.e. the new care-of-address, is known and has been updated in the home gateway. If the interruption time for the change exceeds the time-out delays specified e.g. in the TCP (Transfer Control Protocol) for dead times, the IP connection is interrupted. Even when the interruption time lies within the time-out delays specified in the TCP, however, the IP applications are not able to maintain the connection if a network interface is not permanently available and uninterrupted. This leads to the IP applications having to be restarted normally when a mobile node switches between two different network interfaces in order to be able to access a particular IP data tunnel.
Another problem is that, on the side of the mobile node, the data packets get lost in downtime between the connections since no physical network device is assigned anymore. This is particularly problematic in point-to-point connections, such a VoIP, that require uninterrupted data transfer.